Method and Wireless Transmit/Receive Unit for Supporting an Enhanced Uplink Dedicated Channel Inter-Node-B Serving Cell Change

1. A method of supporting a serving cell change from a source Node-B to a target Node-B implemented in a wireless transmit/receive unit (WTRU), the method comprising: receiving from the source Node-B a plurality of resource allocations associated with a first serving cell; transmitting, in response to the receipt of the plurality of resource allocations from the source Node-B, a first sequence of protocol data units (PDUs) to at least the source Node-B, wherein each PDU is assigned a respective sequence number; receiving a radio resource control (RRC) message indicating a serving cell change from the source Node-B to the target Node-B, wherein the source Node-B is a single Node-B and the target Node-B is a single Node-B, wherein the serving cell change is an enhanced uplink dedicated channel (EU-DCH) inter-Node-B serving cell change; receiving from the target Node-B a plurality of resource allocations associated with a second serving cell in response to the received RRC message; setting an indicator for transmitted PDUs that have not been acknowledged by the source Node-B; transmitting, in response to the receipt of the plurality of resource allocations from the target Node-B, a second sequence of PDUs to at least the target Node-B, wherein each PDU corresponds to a PDU in the first sequence indicated as not being acknowledged by the source Node-B, and each PDU maintains the same sequence number assigned to the corresponding PDU in the first sequence; and transmitting a message indicating completion of the EU-DCH inter-Node-B serving cell change.

2. The method of claim 1 further comprising: sending a message to a serving radio network controller (S-RNC) indicating that the serving cell change has been completed.

3. A wireless transmit/receive unit (WTRU) comprising: a receiver configured to receive a plurality of resource allocations associated with a first serving cell from a source Node-B; a transmitter configured, in response to the receipt of the plurality of resource allocations from the source Node-B, to transmit a first sequence of protocol data units (PDUs) to at least the source Node-B, wherein each PDU is assigned a respective sequence number; the receiver further configured to receive a radio resource control (RRC) message indicating a need for a serving cell change from the source Node-B to a target Node-B, wherein the source Node-B is a single Node-B and the target Node-B is a single Node-B, wherein the serving cell change is an enhanced uplink dedicated channel (EU-DCH) inter-Node-B serving cell change; the receiver further configured to receive a plurality of resource allocations associated with a second serving cell from the target Node-B in response to the received RRC message; a processor configured to set an indicator for transmitted PDUs that have not been acknowledged by the source Node-B; the transmitter further configured, in response to the receipt of the plurality of resource allocations from the target Node-B, to transmit a second sequence of PDUs to at least the target Node-B, each PDU corresponds to a PDU in the first sequence indicated as not being acknowledged by the source Node-B, and each PDU maintains the same sequence number assigned to the corresponding PDU in the first sequence; and the transmitting further configured to transmitting a message indicating completion of the EU-DCH inter-Node-B serving cell change.

4. The WTRU of claim 3 wherein the transmitter is further configured to send a message to a serving radio network controller (S-RNC) indicating that the serving cell change has been completed.